Toward Comprehensive Modeling and Large-Angle Tracking Control of a Limited-Angle Torque Actuator With Cylindrical Halbach

The single-phase limited-angle torque (LAT) motor with cylindrical Halbach magnetic array provides a smaller form factor, lighter moving mass, and higher force throughput within
$\pm$
60
$^\circ$
angle range, compared with the three-phase permanent magnet synchronous motor. Due to the imperfect flux distribution within the air-gap of the Halbach array, as well as the inherent angular dependent characteristics, it is mainly used for point-to-point motion applications in prior literature. In this paper, we would like to deal with above issues, so that it can be extensively used for large-angle tracking applications. First, we derive the ideal model of this LAT actuator. Next, we propose to identify its nominal model parameters by the relay feedback with sufficiently small oscillations near the neutral position. Later, a robust output feedback control with high-gain observer is proposed to handle both model uncertainty and angular-dependent nonlinear current–torque relationship, so that the precision tracking of a defined smooth trajectory is achieved with only position sensing. The real-time experiment on a prototype validates the practical appeal of proposed methods.